Materials
Here is a complete listing of the materials that I have used and recommend in finishing 3D prints. I have listed these materials into two categories, Essential and Optional.
Essential
These are the tools that you should always have in your kit.
Paper Towels For cleaning spills, of course, but also for applying paint.
Used Toothbrushes For creating randomized spot effects (splatter)
Inexpensive Spray Primer (Flat White, Flat Grey, Flat Black)
Spray Acrylic Paints (Whatever colors you need at the time. Yellow, Red, Blue, Green, Brown, Black, White and a few metallic colors are good to have on hand all the time. I recommend acrylic over enamel simply because acrylic is less of an issue when spraying, however, if you have a good area like the outdoors or a spray booth with outtake fans, enamels work well, too. Get the least expensive ones you can find. Since most of the time you will be laying down a clear coat, the less expensive will not be subjected to stress from handling over time.)
Badger or Createx Airbrush Acrylics (pre-thinned and excellent for modeling)
Goop I have tried a large amount of adhesives in my quest to assemble multi-part prints with strong bonds. This is what I have found to be the most effective. I had a print of a T-Rex skeleton fall off the roof of a moving car and not one of the places where the print was glued broke or came undone.
Talcum Powder for creating flat finish paints from glossy finish paints. It can also be used to create snow effects.
Optional
Paasche VL Airbrush For a lot of advanced modeling work, this tool will become an essential. For those who are planning on working on advanced techniques, place this in the Essential column.
Air Compressor There are a lot of compressors out there that will do the job for you. I link to the Badger, because I have used one for nearly 25 years and it still runs like a trooper and is a reasonable price. Obviously, this too becomes an essential item if you plan to use an airbrush in your modeling.
Steel Wool (for polishing prints, especially those of metal based filaments, or simply adding metal shavings to a model that requires that look)
Cotton Balls
Glass Beads These little beads are a sanitary way to add textures to your prints. Or to simply apply a reflective effect. I glue them on with Elmers glue, then paint.
Inexpensive Soldering Iron This tool has a multitude of uses, from welding together seams in a print, to sculpting out details not modeled in the print.
Lichen comes in many colors and can be used to add foliage to your model. Shrubs, bushes, trees can all be quickly created and look quite realistic.
Wen Rotary Tool This is great for polishing and cleaning up a print. Also, it can be used to add detailing to a model.